1892.] 



CLA.SSIFICATIOX OF BIRDS. 



231 



Of course this merely mathematical principle is scientifically faulty, 

 because the characters are decidedly not all equivalent. It may 

 happen that a great numerical agreement between two families rests 

 upon unimportant characters only, and a small number of coincidences 

 may be due to fundamentally valuable structures, and in either case 

 the true affinities would be obscured. This it was necessary to 

 inquire into. But at any rate I obtained many hints from this 

 simple mode of calculation, indicating the direction which further 

 inquiry should take. 



The Psittaci may serve as an example of my mode of sifting 

 characters. 



According to the numerical agreement of the 40 characters 

 employed generally, we have the following table : — 



Psittaci agree with Coccyges in 31 points, with Pici in about 29, 

 with Coraciidee 25, Falconidse 23, Striges 22, Bucerotidse 22, 

 Gallidse 21, against 19 points of difference. 



A previous line of investigation had revealed the fact that the 

 Coccyges and Gallidse are intimately connected with each other 

 through Opisthocomus. This knowledge obviated further inquiry as 

 to the affinity between Psittaci and Gallidae. 



I. Comparison of Psittaci with Falconidce. 



Psittaci and Falconidce agree, 



Nidicolous = Cuculi, 



Woolly nestlings. 



Distribution of nestling downs. 



Distribution of adult downs. 



Cervical apteria = Oueuli. 



Dorsal apteria = Coccyges. 



Ventral apteria = Musophagidse. 



Aftershaft = Musoph. 



Tufted oil-gland = Musoph. 



Aquinto-cubital. 



Desmognathous = Cuculi. 



No basipteryg. proc. — Cuculi. 



Holorbinal = Cuculi. 



Nares imperpise = Cuculi. 



Shallow temporal fossa. 



Number of cervical vertebr8e= Cuculi. 



No spina interna = Cuculi. 



Spina externa = Cuculi. 



Posterior sternal margin = Cuculi. 



Coraeoids = Cuculi. 



Furcula = Cuculi. 



Humero-coracoid groove = Cuculi. 



Cervical hasmapojDhyaes = Cuculi. 



2 carotids = Cuculi. 



Tongue. 



Intestinal convolutions. 



Pdittaci and FalconidcB differ. 



Toes = Cuculi (not Pandion). 



10 remiges = Cuculidas. 



No vomer = Musophagidse. 



Mandible = Musoph. 



4-Ectepicondylar process = Cue. 



+Tibial intercondylar tubercle=:Cuc. 



Hypotarsus complex = Cue. 



Flexor tendons = Cue. 



Garrod's formula = Cue. 



Large procoracoid process = Cue. 



Thoracal hsEmapophyses = Cue. 



Food = Musoph. 



Casca none = Musoph. 



Syrinx specialized. 



14 negative points. 



26 positive points. 



cations within the various members of such groups, as, e. g., Tubinares and 

 Accipitres, Limicolte and Passeres. These are traps which it is not always 

 easy to avoid. 



